1. Field of the Invention
The present invention generally relates to holders for rectangular-shaped objects such as printed circuit boards (PCBs) or printed circuit cards having electronic components mounted thereon, and more particularly to guides having a "snap lock" mechanism for guiding and holding printed circuit boards or cards therein. The card guide is designed for installation in a card guide enclosure, rack, chassis or other suitable housing to hold the cards in a spaced, parallel array. The "snap-lock" mechanism of the present invention allows a card guide frame to be easily inserted into a rigid U-shaped enclosure and for the cards to be reliably held in the card guide frame.
2. Description of the Related Art
Holders and guides for PCBs are known and are useful for storing and protecting the PCBs. Racks for holding electronic gear have heretofore been relatively complex, have included large numbers of separate parts and fasteners, and have required a great deal of labor to assemble.
For example, as shown in FIG. 8, a conventional card guide includes upper and lower frame portions, each of which includes a plastic frame 61 having at respective ends thereof pairs of legs 62 which are snap-fitted onto a horizontal rail 63 having been previously attached to an enclosure (not shown) via threaded screws 64 and washers 65. A printed circuit card is adapted to be inserted into the guide in a slot formed in the plastic frame. To accommodate the length of the card, typically a pair of frames 61 are arranged horizontally (i.e., on the same plane) on the enclosure surface. Frames 61 are also designed to be used in tandem with a pair of second like frames 61 parallel to the first pair of frames such that the slots of the upper and lower frames oppose each other respectively. Thus, for each plastic card guide a total of four frames are used to guide and hold a printed circuit card. However, the conventional plastic card guide has various problems.
First, the plastic card guide requires a relatively large number of pans, thereby resulting in poor assembly efficiency and increased cost. Indeed, the large number of parts (i.e., washers, screws, etc.) increases the chances of inadvertently leaving some out during assembly or that some of the parts may become lost, and further one or more of the parts may become stripped or loosened during assembly. Further, the plastic card guide has poor reliability in that the plastic card guide has a tendency to break when cards are inserted or removed therefrom at extreme angles. Moreover, during assembly the plastic card guides may be placed in the wrong slot (unless a special fixture is designed and built), in which case the plastic card guides are difficult to remove without breaking. Further, the horizontal rails which hold the plastic card guides are difficult to align, absent a specially manufactured fixture.
Another conventional card guide, as shown in FIG. 9, is a screw-in card guide which includes upper and lower frame portions, each of which includes an integrally formed metal frame 71 having a bottom panel 72 with vertically extending side walls 73 at first and second ends of the bottom panel. Openings 74 are provided for airflow therethrough. The screw-in card guide is fixed to an enclosure (not shown) by screws 76 and washers 77. Clinch-nut fasteners are used to attach (using screws or the like) the card guide to a backplane. Frame 71 is also designed to be used in tandem with a second like frame 71 parallel to the first frame such that the slots of the upper and lower frames oppose each other respectively. Thus, for each screw-in card guide a total of two frames, as well as a plurality of screws, etc., are required for guiding and holding a printed circuit card.
The screw-in card guide has several advantages over the plastic card guide described above. For example, the screw-in card guide requires much less parts than the plastic card guide and therefore assembly time is decreased and assembly efficiency is increased. However, the screw-in card guide still has the problems associated with using screws for assembly, as discussed above.
U.S. Pat. No. 4,530,033 to Meggs discloses yet another conventional card frame for printed circuit cards. The card frame includes molded plastic panels 2 and molded plastic sidewalls 1 adapted to be coupled to the panel. The panel includes U-shaped tenons 21 for insertion into openings 14 in the sidewalls 1 by moving the tenons 21 perpendicularly to the sidewalls and sliding the tenons into place along locating tongues 141 and ridges 142 disposed in the openings. The panel has an elastic tongue 22 for deflection along ramps 15 disposed between pairs of tenons 21 at the ends of the panels. When the panels are slidably positioned (i.e., the elastic tongues snap back to their initial or rest position), the free edges of the elastic tongues abut an end of the ramps to lock the panels onto the sidewalls.
The design of the card frame of U.S. '033 has various problems. For example, the locking mechanism of the card frame of U.S. '033 does not allow a card guide frame to be easily inserted into a rigid U-shaped enclosure. Further, the design of the card frame of U.S. '033 is only for plastic and it would be difficult to use metal for the panels of U.S. '033 because the locking structure of U.S. '033 relies on the relative flexibility and resiliency of the plastic tongues, etc. Further, molding the parts of U.S. '033 from metal in lieu of plastic would be complicated and expensive in terms of the molding process itself, and thus impracticable. Additionally, the system of U.S. '033 requires a plurality of components (i.e., four) for assembly, thereby making assembly cumbersome and time-consuming.